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Hops
Hop Products
Besides whole hops (hop cones), other hop products are used. The international hop industry currently recognizes four general types of hop products. They are nonisomerized hop products, isomerized hop products, and hop oil products. The ones most commonly traded in the commercial market are pellets and extracts. Hop products offer brewers several distinct advantages over fresh hops. They exhibit a more consistent chemical composition over time and provide brewers with a more manageable and utilizable form of hops that occupies less space.
Isomerized Hop Products
With isomerized hop products, the alpha acids have been isomerized to iso-alpha acids during processing. As a result, they can be added to the kettle not only during wort boiling, but also – unlike alpha-based products – during the maturation phase. Products included in this group are as follow . Isomerized hop pellets are basically conventional Type 90 pellets in which the alpha acids have been converted to iso-alpha acids. The major benefit to the brewer of using isomerized hop pellets is a significant increase in utilization of the bittering component. Isomerized pellets can be added at any stage of boiling while maintaining high utilization. Consequently, late additions of aroma hops optimize utilization of the alpha acids not usually converted with typical hop aroma late kettle additions.
NonIsomerized Hop Products
The alpha acids are unchanged during processing nonisomerized products. As a result, the products can be added to the kettle only during wort boiling. Products included in this group are listed below.Hop plugs (Figure 3.2) are used in the United Kingdom as a convenient means of dry hopping cask-conditioned ales. The hop plug is technically a Type 100 pellet, and is made by compressing whole hops (unground) into a plug that measures between 10 and 30 mm in thickness, depending on the weight.Hop pellets (Figure 3.3) are nothing more than whole hops mechanically processed by a hammer-mill and pelletizing machine. The pellets are held together naturally by their own oils, resins, and moisture content. The alpha acid rating (and, if available, the oil content rating) is determined after the pelletizing process. Craft brewers commonly use hop pellets to the exclusion of hop extracts.There are actually several types of hop pellets on the market. The most common is the regular or standard (Type 90) pellet, which is whole hops ground and pelletized.Another type of pellet on the market is the concentrated (Type 45) hop pellet, also called "enriched" pellets. This type is derived from a process in which hop petals are mechanically separated from resins and oils at subfreezing temperatures (-35ºC).In stabilized pellets, magnesium oxide is mixed in with the hop powder, then the mixture is pelletized. The addition of magnesium oxide gives the pellets greater storage stability than Type 90 pellets.
Hop Oil Products
Pure hop oils usually have a very pale green/yellow appearance. They have been on the market for many years, and give beer hop aroma without imparting any bitterness. Traditionally, hop oils are added to the kettle late in the boil, which is known as "late hopping," or they are used for dry hopping. It is generally agreed that the addition of hop oil to filtered beer does not produce a satisfactory flavor since some contact time with yeast is necessary to remove "raw hop," "tobacco," and "grassy" notes.
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